In order to contend with ongoing physiological stress imposed by the local microenvironment or by endogenous oxidative processes, cells have evolved a complex network of signaling molecules to detect these perturbations and to recruit an ensemble of responses to countermand the insult. These afferent signals converge on a host of transcription factors that coordinately regulate the expression of genes which give cells pause to rectify the cellular injury or to execute an apoptotic program. Arguably, the most ubiquitous source of environmental stress for terrestrial organisms is ultraviolet radiation (UVR) and the most lethal consequence of this widespread exposure in human is malignant melanoma. The success of the aspiring melanoma cell is critically dependent on its ability to negotiate the physiological challenges of early UVR threat. In order to better understand these early events, we recently set out to identify UVR-inducible genes in primary pigment cells. In preliminary studies, we discovered that the receptor tyrosine kinase, EPHA2, is upregulated by UVR in melanocytes and other cells types and by a common melanoma oncogene, activated NRAS. Most notably, EphA2 appears to be an essential mediator of apoptosis in response to UVR - the most common exogenous stressor for these cells. In this application, our overarching goal is to understand the role of EphA2 in regulating the UVR stress response and potential downstream tumorigenesis. In the first two Aims, we will explore the mechanism by which EphA2 induces apoptosis and expand on its position as a UVR stress-inducible gene in intact skin. In the last Aim, we will investigate the link between UVR stress and oncogenesis in a novel murine model of melanoma photocarcinogenesis. PROJECT NARRATIVE. Malignant melanoma is possibly the most lethal consequence of long-term ultraviolet radiation (UVR) stress and mutagenesis. In preliminary studies, we identified a UVR stress-inducible gene, EPHA2, which empirically behaves as an essential mediator of UVR-induced apoptosis. As this gene has been implicated in the pathophysiology of multiple cancers, we propose to elucidate the mechanism by which EPHA2 modulates cellular death or survival. These clues will undoubtedly drive therapeutic developments in metastatic melanoma, which, to this day, remains incurable.